package com.baidu.captcha;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.security.MessageDigest;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletOutputStream;

import com.jfinal.kit.StrKit;
import com.jfinal.render.Render;


/**
* 验证码Render，这个验证码Render在构造函数里就已经创建好了随机码以及md5散列后的随机码。
* 调用方式如下：
* CaptchaRender captchaRender = new CaptchaRender();
* String md5RandonCode = captchaRender.getMd5RandonCode();
* 保存md5RandonCode到session、cookie或者其他地方
* render(captchaRender);
* 基于JFinal的版本修改。
*
*/
public class CaptchaRender extends Render{
   /**
    * 随机码生成字典
    */
   private static final String[] strArr = {"3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F", "G", "H", "J", "K", "M", "N", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y","Z"};


   /**
    * 默认存储时使用的key,将md5散列后的随机码保存至session，cookie时使用。
    */
   public static final String DEFAULT_CAPTCHA_MD5_CODE_KEY = "_CAPTCHA_MD5_CODE_";

   /**
    * 图片宽度
    */
   private final int imgWidth;

   /**
    * 图片高度
    */
   private final int imgHeight;

   /**
    * 随机生成字符数量
    */
   private final int imgRandNumber;

   /**
    * 生成的随机码
    */
   private final String randonCode;

   /**
    * md5散列后的随机码
    */
   private final String md5RandonCode;

   /**
    * 构造函数,随机生成4个字符。
    */
   public CaptchaRender() {
       this(4);
   }

   /**
    * 构造函数
    * @param imgRandNumber 随机生成多少个字符,最少4个字符。
    */
   public CaptchaRender(int imgRandNumber) {
       if(imgRandNumber < 4)
       {
           imgRandNumber = 4;
       }
       this.imgWidth = 16*imgRandNumber + 12;
       this.imgHeight = 26;
       this.imgRandNumber = imgRandNumber;
       this.randonCode = generateRandonCode();
       this.md5RandonCode = encrypt(randonCode);
   }

   /**
    * 获取md5散列后的验证码，调用发需妥善保存此验证码。
    * @return md5散列后的验证码
    */
   public String getMd5RandonCode(){
       return this.md5RandonCode;
   }

   /**
    * 依据字典生成随即码
    * @return 随机码
    */
   private String generateRandonCode(){
       // 生成随机类
       Random random = new Random();
       String sRand = "";
       for (int i = 0; i < imgRandNumber; i++) {
           String rand = String.valueOf(strArr[random.nextInt(strArr.length)]);
           sRand += rand;
       }
       return sRand;
   }

   /**
    * 渲染图片
    */
   public void render() {
       BufferedImage image = new BufferedImage(imgWidth, imgHeight, BufferedImage.TYPE_INT_RGB);
       drawGraphic(image);
       response.setHeader("Pragma","no-cache");
       response.setHeader("Cache-Control","no-cache");
       response.setDateHeader("Expires", 0);
       response.setContentType("image/jpeg");

       ServletOutputStream sos = null;
       try {
           sos = response.getOutputStream();
           ImageIO.write(image, "jpeg",sos);
       } catch (Exception e) {
           throw new RuntimeException(e);
       }
       finally {
           if (sos != null)
               try {sos.close();} catch (IOException e) {e.printStackTrace();}
       }
   }

   /**
    * 绘制验证码
    * @param image BufferedImage对象
    */
   private void drawGraphic(BufferedImage image){
       // 获取图形上下文
       Graphics g = image.createGraphics();
       // 生成随机类
       Random random = new Random();
       // 设定背景色
       g.setColor(getRandColor(200, 250));
       g.fillRect(0, 0, imgWidth, imgHeight);
       // 设定字体
       g.setFont(new Font("Times New Roman", Font.PLAIN, 18));

       // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
       g.setColor(getRandColor(160, 200));
       for (int i = 0; i < 155; i++) {
           int x = random.nextInt(imgWidth);
           int y = random.nextInt(imgHeight);
           int xl = random.nextInt(12);
           int yl = random.nextInt(12);
           g.drawLine(x, y, x + xl, y + yl);
       }

       g.setFont(new Font("TimesRoman", Font.PLAIN, 20));
       //取随机产生的认证码(img_randNumber位数字)
       for (int i = 0; i < imgRandNumber; i++) {
           String rand = String.valueOf(this.randonCode.charAt(i));
           // 将认证码显示到图象中
           g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));
           // 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
           g.drawString(rand, 16 * i + 6, 21);
       }
       // 图象生效
       g.dispose();
   }

   /**
    * 生成随机颜色
    * @param fc
    * @param bc
    * @return 颜色对象
    */
   private Color getRandColor(int fc, int bc) {
       Random random = new Random();
       if (fc > 255)
           fc = 255;
       if (bc > 255)
           bc = 255;
       int r = fc + random.nextInt(bc - fc);
       int g = fc + random.nextInt(bc - fc);
       int b = fc + random.nextInt(bc - fc);
       return new Color(r, g, b);
   }

   /**
    * 使用md5散列字符串
    * @param srcStr 输入的字符串
    * @return 加密后的字符串
    */
   private static final String encrypt(String srcStr) {
       try {
           String result = "";
           MessageDigest md = MessageDigest.getInstance("MD5");
           byte[] bytes = md.digest(srcStr.getBytes("utf-8"));
           for(byte b:bytes){
               String hex = Integer.toHexString(b&0xFF).toUpperCase();
               result += ((hex.length() ==1 ) ? "0" : "") + hex;
           }
           return result;
       } catch (Exception e) {
           throw new RuntimeException(e);
       }
   }

   /**
    * 验证码检查
    * @param md5RandomCode  md5散列后的验证码
    * @param inputRandomCode 用户输入的验证码
    * @return 若二者一致，返回true，否则返回false
    */
   public static boolean validate(String md5RandomCode, String inputRandomCode) {
       if (StrKit.isBlank(md5RandomCode) || StrKit.isBlank(inputRandomCode))
           return false;
       try {
           inputRandomCode = inputRandomCode.toUpperCase();
           inputRandomCode = encrypt(inputRandomCode);
           return inputRandomCode.equals(md5RandomCode);
       } catch (Exception e) {
           e.printStackTrace();
           return false;
       }
   }

}
